Mycophenolic acid O-acyl-glucuronide is a metabolite of mycophenolate mofetil. Mycophenolate mofetil (MMF) (brand names CellCept, Myfortic) is an immunosuppressant and prodrug of mycophenolic acid, used extensively in transplant medicine. It is a reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH) in purine biosynthesis which is necessary for the growth of T cells and B cells. Other cells are able to recover purines via a separate, scavenger, pathway and are, thus, able to escape the effect. MMF is a less toxic alternative to azathioprine. (Wikipedia)